The technology of hinges having elongated hinge pins coextensive with a major portion of adjoining edges of hinged bodies or members is well developed. Generally, one body is joined to another by such a hinge so that one body can be swung relative to the other body about the axis of the elongated hinge pin. Not infrequently, a hinge assembly will have some means of retentively positioning the bodies at one or more angles of swing. For example, automobiles usually have a means to resiliently hold doors in an open position.
The Amerock Corporation of Rockford, Illinois sells a self closing hinge, part number BP-7928-26, that incorporates a spring and rubbing block. The first body of the hinge has two support portions for supporting the single elongated hinge pin near its ends. A rubbing block is attached to the first body between the support portions by means of a springy integrally formed flange portion that is L-shaped in section and extends laterally from the first body to entrap the rubbing block. The second body has a tubular portion adapted to receive and retain the central portion of the hinge pin in the bore of the tubular portion. The exterior of a portion of the tubular portion defines a surface that is disposed radially about and substantially coaxial to the longitudinal axis of the hinge pin. The rubbing block is trapped and somewhat compressed between the tubular surface and the first body. The rubbing block is pressed against the tubular surface by the spring portion so that as the hinge is pivoted throughout most of its range the rubbing block provides frictional resistance.
However, when the hinge is pivoted near its closed position, the rubbing block presses into an inclined portion of a concavity in the tubular surface and moves closer to the longitudinal axis of the hinge pin which forces the hinge into its closed position.
The National Manufacturing Company of Sterling, Illinois sells the Super Swing n' Stay cafe door hinge which incorporates a cam and a cooperating protruding knife-like projection to ride thereon. With this hinge assembly lower and upper brackets are attached to a door frame while top and bottom pivots are attached to the top and bottom of a swinging cafe-type door near a vertical edge thereof. The upper pivot holds an upper hinge pin which is journalled in an upper pivot bearing attached to the upper bracket. The lower pivot holds a lower hinge pin, axially aligned with the upper hinge pin, which is journalled in a lower pivot bearing attached to the lower bracket. The spacing between the upper and lower brackets is such that the door can move up and down about one half an inch as the hinge pins slide up and down about one half an inch in the direction of their common axis, and swing from side to side about the axis of the hinge pins. The bottom bracket has an upward facing sliding surface disposed radially about and substantially normal to the axis of the lower hinge pin, which surface is non-planar and in the shape of a cam. The bottom pivot has a dull knife-like projection that rests on the cam. When the door is swung from its normal position, the knife-like projection rotates and rides up the cam raising the door against the force of gravity. When the door is released, the force of gravity on the door causes the knife-like projection to ride the cam downward and the door returns to its normal position, the low point of the cam being positioned relative to the knife-like projection to coordinate with the door closed position.
Problems with prior position retentive hinge assemblies include the excessive number of parts used and difficulties of incorporating the prior concepts into injection molded hinge assemblies.